Tanning process



' used.

Patented Dec. 5, 1933 oNiTED STATES TANNING PROCESS Alphons O.Jaeger,Mount Lebanon, Pa., assignor to The Selden Company, Pittsburgh,Pa., a corporation of Delaware N0 Drawing.

Application February 27, 1931 1 Serial No. 518,901

12 Claims.

This invention relates to the tanning of hides, skins and the like,using a new class of tanning materials.

According to the invention, leather is produced by the tanning of hidesand skins in the presence of a new class of tanning agents, which may beused alone or in admixture with other vegetable or artificial tanningmaterials. The new tanning agents of the present invention are alkalimetal salts of the sulfonated products resulting from the condensationof carbohydrates, phthalic anhydride and substituted or unsubstitutedaromatic hydrocarbons in the presence of sulfuric acid, either pure orcrude materials being These substances are new chemical products but arenot claimed as such in the present application, this forming the subjectmatter of my co-pending application Serial No. 512,753, filed January31, 1931. One of their outstanding features is the presence of phthalicanhydride in combination with the cellulose and aromatic hydrocarbonwhich acts as an improved loading agent, serving to increase the weightand fullness of the leather without materially altering the solubilityin water of the preparation.

As is brought ,out in the application just referred to, these tanningmaterials can be readily prepared from very cheap materials, and arecharacterized by a good light color and excellent tanning properties.They possess rapid penetrating qualities as compared with the vegetabletans and are thus not only valuable tanning agents when used alone butare also well suited for mixture and use with the. ordinary vegetabletans. Being alkali metal compounds, and having a fairly high pH value,they exert a stabilizing action on the ordinary vegetable tanningextracts and prevent them from precipitation by oxidation on exposure tothe air, and they are thus valuable, not only for use as an aid intanning, but alsofor admixture with the vegetable tans beforeshipment.

While the stabilizing action and rapid penetration of the novel tanningagents of the present invention make them valuable aids when used inconjunction with'the less astringent tanning extracts, such as thoseofgambier, oak, chestnut and sumac, these condensation products are ofeven greater value when used in conjunction with the more astringenttans such as quebracho, hemlock and the like. In the process ofvegetable tanning it is well known that the rate of diffusion, andconsequently the rate of tannage is inversely proportional to-thjeastringency of the tan used. Such extracts'as't-hose of quebracho,hemlock, larch, etc. therefore require considerably longer time tocompletelytah the hides than do the less astringent tans such asgambler, probably because the more astringent tans immediately effectsuch a complete tannage at the surface that rapid penetration isretarded. The addition of the tanning materials of the present inventionto the liquors of an astringent vat aids in penetration, not only byacting as a less astringent diluent, but also by the fact that its morerapid penetration effects a partial tannage in advance of the vegetableextract, thus preventing imperviousness of the outer portions of thehide. The invention is not limited however to the use of the noveltanning agents in conjunction with -more astringent tans but on thecontrary their properties are such that they may be used alone or inconjunction with any material having tanning or non-tanning properties.

As has been stated, the tanning agents of the present invention are forthe most part slightly alkaline and usually require the addition ofacids, such as acetic, phosphoric, lactic, etc. to bring the tanningliquors to a value pI-I=25 or thereabouts in order to exert the mostfavorable tanning action. Of course where the tanning agents are used inconjunction with other and more acid materials, allowance for this factwill be made and the hydrogen ion concentration will be adjustedaccordingly.

The invention will be further illustrated in conjunction With thefollowing examples to which, however, the invention is not limited. Theparts are by weight.

Example 1 1500 parts of 100% sulfuric acid are cooled to 20 C. and 70parts pure phthalic anhydride are slowly added. After addition iscomplete, 100 parts cellulose in the form of waste paper or the like areadded with stirring during two hours, and the mixture is further stirredwith cooling for a period of three to six hours.

After the reaction is complete, 268 parts of a residue from thevaporization of semi-purified anthracene with air in the catalyticoxidation of anthracene to anthraquinone are added with constantstirring, the temperature being maintained below 25 C. and the stirringis continued until the reaction is completed. The product is then pouredinto a mixture of 4,000 parts ice and water and stirring continued forone hour, after which milk of lime made from 700 parts CaO is added,followed by sufficient calcium carbonate to complete neutralization. Theproduct is filtered and converted into the sodium salt by treatment withsodium carbonate in the usual manner.

The hides, delimed and bated, are introduced into a tanning bathcontaining 40 grams per liter of the above described condensationproduct together with suitable amounts of oak bark tanning extract,being allowed to remain with suitable agitation after the tanning actionis well started, until complete tannage is effected.

The leather obtained after washing and the usual further treatments, isof good appearance and of excellent strength.

Example 2 '750 parts of 107.3% sulfuric acid are cooled to 20 C. and34.3 parts pure phthalic anhydride, or the equivalent quantity of impurephthalic anhydride, are added. The mixture is further cooled to 16 C.and 50 parts of cellulose in the form of old sulfite paper, cottonlinters or the like areadded during four hours. The mixture is stirredduring a further period of eight hours and is then a blackish liquidsmelling somewhat 0f S02.

To this liquid are added 134 parts of residue from the purification ofcrude anthracene, the addition being made very slowly during a period offive hours and the temperature being kept at all times below 20 C.Stirring is continued until the reaction is complete, the resulting massbeing a deep black, viscous liquid.

The above mixture is poured, with stirring, into 2,000 parts of watermaintained as cold as possible, and milk of lime prepared from 360 partsof CaO is added, after which neutralization is completed with CaCOa.After filtering, the liquid may be evaporated to produce a solidproduct, or the calcium may be exchanged for sodium by treatment withsodium carbonate.

Hides, properly prepared, are tanned in baths of the above condensationproduct, the baths increasing in strength as the period of tannageproceeds. The pH of the tanning bath is adjusted by the addition ofacetic acid, sodium phosphate being added as a buffer if necessary.

Example 3 50 parts cellulosic material in the form of waste paper arestirred into 750 parts 100% sulfuric acid maintained at 15-18 C., afterwhich '70 parts phthalic anhydride are added and stirring is continuedfor ten to twenty hours until reaction is completed. 130-140 partsresidue from the vaporization of impure naphthalene in the catalyticphthalic anhydride process are slowly added with stirring during five toeight hours and the mixture is maintained at 35 C. for fifty to seventyhours until reaction is completed.

The reaction product is slowly poured into a mixture of 1,000 parts iceand 1500 parts water and stirred for one-half hour, after whichneutralization is effected with 300 parts CaO and further amounts ofCaCOa in the usual manner. The product is stirred for one-half hour,filtered, washed, and the calcium replaced by sodium as in previousexamples.

The above condensation product is admixed with an equal weight of freshquebracho, oak or gambler extract as it comes from the leaching vat, andthe mixture is evaporated to the usual commercial strengths (IO-30%moisture content) for sale on the market. The material so produced formsan excellent tanning agent, and precipitation of the vegetable tan byexposure to air, both during evaporation and in the preparation of thetanning liquors, is reduced by thepresence of alkali metal compound.

What is claimed as new is:

l. A process of tanning hides, which comprises treating the hides withan aqueous solution conaining at least one salt of a condensationproduct of a carbohydrate, a phthalic anhydride substance, at least onearomatic hydrocarbon, and sulfuric acid.

2. A process of tanning hides, which comprises treating the hides withan aqueous solution containing at least one alkali metal salt of acondensation product of cellulose, a phthalic anhydride substance, atleast one aromatic hydrocarbon, and sulfuric acid.

3. A process of tanning hides, which comprises treating the hides withan aqueous solution containing at least one alkali metal salt of acondensation product of a carbohydrate, phthalic anhydride, at least onearomatic hydrocarbon, and sulfuric acid.

4. A process of tanning hides, which comprises treating the hides withan aqueous solution containing at least one alkali metal salt of acondensation product of cellulose, phthalic anhydride, at least onearomatic hydrocarbon, and sulfuric acid.

5. A process of tanning hides, which comprises treating the hides withan aqueous solution containing at least one alkali metal salt of acondensation product of a carbohydrate, a phthalic anhydride substance,the residue from the purification of a crude aromatic hydrocarbon, andsulfuric acid.

6. A process of tanning hides, which comprises treating the hides withan aqueous solution containing at least one alkali metal salt of a con-'densation product of cellulose, a phthalic anhydride substance, theresidue from the purification of a crude aromatic hydrocarbon, andsulfuric acid.

7. A process of tanning hides, which comprises treating the hides withan aqueous solution containing at least one alkali metal salt of acondensation product of a carbohydrate, phthalic anhydride, the residuefrom a solvent purification of anthracene with a solvent forphenanthrene and carbazole, and sulfuric acid.

8. A process of tanning hides, which comprises treating the hides withan aqueous solution containing at least one alkali metal salt of acondensation product of cellulose, phthalic anhydride, the residue fromsolvent purification of crude anthracene, and sulfuric acid. 7

9. A process of tanning hides, which comprises treating the hides withan aqueous solution containing at least one alkali metal salt of acondensation product of a carbohydrate, phthalic anhydride, the residuefrom the vaporization purification of semi-purified anthracene, andsulfuric acid.

10. A process of tanning hides, which comprises treating the hides withan aqueous solution containing at least one alkali metal salt of acondensation product of a carbohydrate, phthalic anhydride, the residuefrom the vaporization purification of crude naphthalene, and sulfuricacid.

11. A process of tanning hides, which comprises treating the hides withan aqueous solution containing at least one alkali metal salt of acondensation product of a carbohydrate, crude phthalic anhydride, atleast one aromatic hydrocarbon, and sulfuric acid.

12. A process 'of tanning hides, which comprises treating the hides withan aqueous solution containing at least one alkali metal salt of acondensation product of a carbohydrate, crude phthalic anhydride, theresidue from the purification -of at least one crude aromatichydrocarbon, and sulfuric acid.

ALPHONS O. JAEGER.

